The email address is actually stored in a table. The structure takes data from multiple tables to populate the screen fields. If F1 help shows that the value is in a structure you can use this technique to find the source table. Open F1, click on Technical Information button Double Click on Field name, this displays the structure at the point of the field name Double Click on the Data Element associated with the Field Name, this displays the Dictionary for the data element Click on Where Used icon Box with three arrows, this lists the types of objects the data element can be used in. Tick Table Fields, and execute. In my system this returned 78 tables, yours may be different. Scroll through the tables, till you find one of interest, in this case ADR6 appears to be the one I want. To confirm you can Double click the field name in the table, this displays the Table Dictionary, here click the contents Icon, which launches SE16, here click Number of Entries. If you get a large number, you are probably in the right place.

You can always get a technical developer to help identify the table that are in the structure, which is usually easier, but the above method works.